Typical currently available syringes present a health hazard after use. The needle of the syringe remains protruding from the barrel after use, and if a protective cap is not fitted to the used needle, or such cap is dislodged, the needle can readily puncture the skin of anyone who handles or accidentally treads on the syringe. As several deadly diseases such as human immunodeficiency virus (HIV) and hepatitis C are transmitted by infected bodily fluids which may remain in the needle following a previous use, puncture of the skin by a used syringe can result in the transmission of such deadly diseases.
Transmission of such diseases is a particular problem with intravenous drug users who may attempt to re-use an infected syringe to inject drugs.
Whilst single use needles have been proposed which retract the needle into the hollow barrel after use, such needles are typically cumbersome to operate.